Drilling of wells, and in particular the directional drilling of wells requires continuous measuring of sensed information as to the location of the drill bit, such as inclination of the drill string and drill bit and the angular orientation (azimuth) thereof, so that this critical information may then be conveyed uphole in real time to the drill operator at surface to allow instantaneous adjustments to be made that will ensure the well is being drilled as desired.
For such so-called “measurement while drilling” drilling applications, particularly where the drill bit is rotary steerable, sophisticated battery-powered electronics located in “subs” threadably inserted in the drill string proximate the drill bit sense the desired directional parameters in relation to the drill bit.
Devices such as mud pulsers situated downhole in the drill string and operatively electrically coupled to the downhole electronics, encode the sensed data into a series of pressure pulses. These pressure pulses travel uphole where they are sensed by additional electronic equipment and decoded into the relevant data for the operator to view in real time.
U.S. Pat. No. 9,638,025 entitled “Mud pulser with Poppet Valve, having Linear determination means” and CA 2,463,354 entitled “Intelligent Efficient Servo-Actuator with Sensor for Downhole Pulser” respectively describe two such mud-pulser units for use in such mud-pulse telemetry which have an electric motor therein which regulates/moves a servo-valve to create the desired mud pulses by which the encoded data is sent uphole.
Due to downhole electronics and electrically-powered servo-motors of mud pulsers all requiring battery power, it is necessary that batteries situated downhole in a drill string continually supply high power and have long life to thereby avoid having to frequently “trip out” the drill string to replace batteries in the drill string. “Tripping out” of a drill string is not only expensive but also very time consuming, and it is thus desired that the battery life be as long as possible to reduce the frequency of having to ‘trip out’ the drill string.
Disadvantageously the aforementioned high pressure pulses continually generated downhole for the purposes of mud pulse telemetry create large vibrational forces which detrimentally affect downhole electronics and batteries.
Some prior art “packaging” systems for MWD electronics have been created to attempt to isolate downhole MWD electronics from vibration and shock forces during drilling which act on the housing within the drill string.
For example, U.S. Pat. No. 4,547,833 entitled “High Density Electronics Packaging System for Hostile Environment” is one such packaging system which utilizes annular shoe supports provided on the chassis to isolate such electronics from axial vibrations and axial forces.
However, during drilling operations, particularly at the greater and greater depths and lengths of deviated wells, drill-string “wind-up” can be extensive and effectively cause the drill string to act like a rotary spring. Once torque has been applied to the drill string to allow the drill to operate and drill, backing off the downhole pressure applied to the bit (“weight on bit”) even momentarily can result in the drill string effectively becoming unsprung and large torsional acceleration forces being applied to MWD equipment, potentially exceeding 100 g, as the drill string unwinds.
US 2016/0053557 entitled “Torsional Isolator” is a device which attempts to reduce (axial) vibration and shock during directional drilling inflicted on electronics. Such device, however, is not directed at reducing torsional acceleration forces per se. Rather, the torsional isolator of US 2016/0053557 allows the drill string electronics to oscillate at a slower rotational velocity than the data acquisition rate of the associated sensors such that the sensor records only an average value of azimuth heading and thereby purportedly allows for a higher accuracy measurement of the azimuth heading by the downhole sensor.
The above background information and description of prior publications is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended nor should be construed that any of the above below publications and information provided below constitutes prior art against the present invention.